Tuition Assistance (TA) is a military-sponsored program that reimburses military members for 75% of the tuition costs of college classes while on active duty in the hope of making military service more attractive to young people and encouraging them to remain in the military. TA's effectiveness was examined by using two models--a bivariate probit model of TA usage and reenlistment and a model comparing the re-enlistment decisions of a group of TA users to those of a similar group of nonusers--to analyze tuition assistance and retention behavior for first-term members of the Navy and Marine Corps. The overall usage rates for TA during the first term were 8% in the Navy and 13% in the Marine Corps. Women were 6% more likely to use TA than men were. Age made no difference in TA usage. Aptitude made a difference in TA usage in the Navy but not in the Marine Corps. Service members with family responsibilities were 2-3% less likely to use TA. Re-estimations of the Boesel and Johnson retention model, Garcia and Joy continuation model, and Garcia et al. continuation model are appended, along with the bivariate probit model of TA usage and reenlistment. (Contains 16 tables and 24 references.) (MN)